Nematodes Nabbed

By Nancy Holbert

Like all successful superintendents, Mike Combs understands the interrelation of production variables and their combined effect on turf quality. Fertility influences disease and weed control, and vice versa. Then there are insects, varietal selection, mowing and irrigation programs, and an often unpredictable Mother Nature to contend with. All the variables must roll together to raise the healthy, high-quality turf demanded by today's competitive golf industry.

But in 2003, Combs ran into a mystery at Orchard Hill Country Club in Washongal, Wash. Situated close to the Columbia River, the 18-hole private par-70 facility boasts 10 par fours, three par fives and five par threes. The course was built in two stages: The front nine holes were designed and built by George Junor in 1929, while the back nine, designed by Bill Sanders, were constructed 40 years later.

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The mystery manifested itself when significant anthracnose pressure appeared on a couple of his Poa annua/bentgrass greens. Cut at 0.13 of an inch, the greens are complemented by ryegrass/Poa annua/and bentgrass fairways, collars and tees.

PUZZLING PROBLEM

“I had experience with the anthracnose control program we were using and I knew it would do an outstanding job — which it did, every where but on these particular greens,” Combs explains. “The anthracnose pressure in these areas was so high that we were ready to strip the turf, fumigate the sand and re-sod if we didn't get it turned around quickly.”

His first thought was that nitrogen levels on the stricken greens might be low, predisposing the unthrifty turf to disease pressure. He then conducted several soil tests, comparing the nutrient levels from affected areas of the green to an unaffected area of the same green and an unaffected green. The results showed the nutrient levels to be “almost identical. It was puzzling,” he says.

Subsequent soil tests for nematodes helped solve the mystery and revealed that high populations of lesion, root knot and ring nematodes were at the root of the problem. The parasitic, microscopic worms completely destroy the root system of infected plants, disrupting nutrient uptake, lowering overall plant hardiness and opening the turf to anthracnose infection.

Because anthracnose and nematode damage have similar visual symptoms, diagnosing the problem was complicated. Roots of anthracnose-infected and nematode- damaged plants are blackened and stubby, often appearing cropped off. Anthracnose infects the crown of the plant, spreading upward, leaving blackened tissue in its wake as it spreads through the plant. Eventually, dead reddish-brown or bronze-colored patches appear that can expand several square feet as the fungus progresses. Nematode damage appears as yellowing, wilting, brownish irregular shaped patches that may enlarge slowly over time, killing grass under heavy pressures.

SIMILAR SYMPTOMS DELAY DIAGNOSIS

“The similar symptoms made it difficult to realize we were dealing with two issues at once, which delayed the diagnosis and subsequent treatments,” Combs says. “It took a couple of weeks from our first noticing anthracnose until the nematode diagnosis. The damage increased significantly during that time period.”

He adds that the heavy nematode pressure may have been the result of several factors occurring simultaneously. “Obviously, we always have some nematode population and we must have given them an ideal breeding ground at some point,” he muses. “We may have had slightly low nutrient levels, weakening the plant to the point it made the situation more pronounced. We also had hot, dry weather a couple of seasons ago, and were having problems with a faulty irrigation system. All the factors combined to make conditions conducive to increased nematode populations.”

To further complicate the problem, symptoms for both issues — nematode and nitrogen depletion — are more apparent in hot weather when damaged roots cannot take up nutrients and water. Once diagnosed, the nematodes were effectively controlled with Nemacur nematicide. Combs notes that treatment gave the root system the opportunity to recover from the earlier damage.

The resulting increased turf vigor provided an advantage for his fungicide treatment of 4 ounces of Chipco Signature fungicide mixed with 4 ounces of Daconil per 1,000 square feet. The tank mix is applied every 19 days throughout the summer season.

“Signature provides outstanding anthracnose control,” Combs explains. “The only places we had problems this season were where we still had some nematode pressure. Once we got rid of them and upped our nitrogen, the program was able to do its job. The result was healthier, stronger turf. I rate this program as the number one factor in our success, followed by fertility.”

STRINGENT FERTILITY PROGRAM

Combs adheres to a “stringent” fertility program. One-half pound of nitrogen per 1,000 square feet per month is applied to greens throughout the season in weekly applications. Three weeks of foliar sprays are followed the fourth week with a granular application.

He also makes weekly applications of magnesium, calcium and potassium. Eco Calex 1-0-0 with eight percent calcium, Eco K 1-0-23 and Eco Magnesium with four percent magnesium round out his fertility requirements.

Combs points to membership compliments on turf quality as evidence of the success of his program. “Our turf is lush, green and healthy and that keeps our members happy,” he notes. “We like that.”